This invention relates generally to alarm systems and more particularly to an alarm system for detecting motional disturbances of objects desired to be maintained in a stationary state.
There currently exists a need for a motion responsive alarm system which can be utilized in a variety of applications ranging, for example, from outdoor use to protect unattended vehicles and a variety of non-vehicular property such as construction materials and the like to indoor use in connection with numerous items such as vending machines and the like. In either event, system requirements include a sensor package providing motion detection sensitivity to cover all space in three dimensions and preferably a sensor package mountable in any orientation without requiring adjustment, a circuit design for processing the sensor output in a manner so as to reliably distinguish between minimal movements of an acceptable nature and movements of a more aggravated type and a signal unit adaptable to the particular property/items being monitored and capable of providing both visual and audible alarm indications.
In addition, the circuit design should be of a type which dissipates minimal energy when in the armed mode yet remains active and capable of processing sensor output data. The latter characteristics are highly desirable in the case of portable alarm systems of the type contemplated by the present invention, where extended use in various environments may be required.
Various systems have heretofore been provided for detecting motional disturbances of normally stationary objects such as unattended vehicles and the like. These systems are normally directly attached to the monitored vehicle and employ various sensor and circuitry arrangements to detect unauthorized movements. Typically, due to the design of the sensor arrays utilized, the prior art units must be affixed to the vehicle in a particular spatial orientation or, when a multi-positional device is employed, certain adjustments must be made to properly initialize the unit. Furthermore, although the prior art sensor arrays generally exhibit adequate sensitivity to motion in a particular direction, they do not provide sufficient detection sensitivity to motion in other directions. These deficiencies limit the operational usefulness of prior art systems at the point of basic criticality in an alarm system, the sensing function.
Prior art attempts to provide means for distinguishing between relative levels of motional disturbances have likewise not been altogether satisfactory. Counters are frequently employed but this technique fails to account for the relationship between the sensed disturbance and its time duration. The circuitry of prior art systems are further deficient in that they generally are passive when in the armed mode thereby being rendered unable to accomplish their logic function.